Organic circuits are being investigated because of their promise of providing very low cost circuits for such uses as identification tags, electronic bar codes, and indicators. The low cost arises from their operational characteristics as semiconductors when formed in an amorphous material state, which can be achieved by printing techniques similar to those in wide use today for passive graphic arts and membrane printing (e.g. gravure, flexography, intaglio, screen printing, micro dispensing, micro contact printing, and lithographic printing). However, the present state of printed circuit electronics introduces limitations for circuitry design. The most severe limitations of printed organic electronics are: low on/off ratio (100 to 10,000), significantly large positive threshold voltage (that cannot be controlled by doping, as it typically is in inorganic circuits), and p-channel FETs only (n-channel FETs are not presently compatible with printing technologies). Such limitations are not usually addressed in the art of crystalline and semi-crystalline semiconductors, because such issues are virtually unknown in conventional semiconductor technologies. Due to the present limitations of organic semiconductor devices, conventional circuit design rules (e.g., CMOS logic) cannot be directly applied. For example, two-transistor p-channel inverter designs are not known that result in useful logic circuitry because voltage inputs and outputs are not compatible with one another.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.